AT&T, Apple slapped with suit over visual voicemail

Klausner Technologies has sued the two companies, claiming one of the signature features of the iPhone violates two of its patents.

While many patent cases have little prior case law to work with, the firm has already litigated successfully with two other companies who later licensed the technology. Both Vonage and AOL have struck agreements with the company.

Filed in US District Court for the Eastern District of Texas, the suit asks for damages and future royalties estimated to be $460 million. It has also filed separate cases against Comcast, Cablevision, and Skype parent company eBay for royalties totaling $300 million.

All of Klausner's defendants are acuused of violating Klausner's patents in the voice mail field. In the case of the non-iPhone defendants, all their systems allow users to select which voicemails they would like to hear through an on-screen display -- a method which Klausner says its portfolio already covers.

"We have litigated this patent successfully on two prior occasions," Klausner's legal counsel Greg Dove said in a statement. "With the signing of each new licensee, we continue to receive further confirmation of the strength of our visual voicemail patents."

Technology pundit Larry Dignan was one of those people equivocating Klausner to the infamous patent holding company. "Translation: Hey it worked twice already why not extract more cash. These things add up," he wrote in a blog entry Monday.